Oil spills due to releases of crude oil from tankers, offshore platforms, drilling rigs, and wells, as well as spills of refined petroleum (such as gasoline or diesel) and their by-products, and heavier fuels used by large ships such as bunker fuel, if uncontrolled may have devastating and lasting environmental impact. Such spills may be controlled by chemical dispersion, combustion, mechanical containment, and/or adsorption. Controlled burning can reduce the amount of oil in water, but can only be done in low wind conditions. Dispersants create smaller oil droplets which may be scattered by currents, and may degrade more easily. Dry hydrophobic, water insoluble polymers that both adsorb and absorb hydrocarbons can clean up oil spills by changing the physical state of oil from liquid to a semi-solid or a rubber-like material that floats on water, rendering it readily collectable. However, collected solidifiers must be disposed of in landfills, recycled as an additive in asphalt or rubber products, or burned as a low ash fuel. Oil-absorbing materials such as hair and fabrics may also be used. Oil may be “vacuumed” from the surface, along with some water, and the mixture centrifuged to separate the oil from the water, thereby permitting nearly pure oil to be collected, the water often being returned to the sea. Oil skimming devices may also be used.
Typically, large floating barriers, known as booms, are used to surround and confine an oil slick, thereby enabling chemical and biological agents to be added to the oil to encourage its breakdown, and mechanical techniques to be used more efficiently.